An ignition system (10) comprises a high voltage transformer (12) comprising a primary winding (12.1) and a secondary winding (12.2). A primary resonant circuit (26) is formed by the primary winding (12.1) and a primary circuit capacitance (24). A secondary resonant circuit (16) is formed by an ignition plug (14), as a load, the secondary winding (12.2); the ignition plug (14) being represented by a secondary circuit capacitance (18) and a secondary circuit load resistance (Rp) put in parallel. Said load resistance value varies during an ignition cycle. The primary resonant circuit (26) and the secondary resonant circuit (16) have a common mode resonance frequency (f.sub.c) and a differential mode resonance frequency (f.sub.d). A controller (28) is configured to cause a drive circuit (22) to drive the primary winding at a frequency, which is either the common-mode resonance frequency (f.sub.c) or the differential mode resonance frequency (f.sub.d) and is connected to a feed-back circuit (50) to adapt the frequency of the primary winding to the variable load resistance.

An ignition unit improves an air-fuel-ratio, i.e., good mileage and lean burn without changing a gasoline engine structure significantly. The ignition unit comprises a discharge device including a booster and a discharger provided at an output side of the booster, the booster having a resonance structure configured to boost the electromagnetic wave inputted from the electromagnetic wave oscillator so as to cause a discharge from the discharger, and an electromagnetic wave emitter electrically connected to the electromagnetic wave oscillator and configured to emit the electromagnetic wave inputted from the electromagnetic wave oscillator. Moreover, the ignition unit further includes a housing part including a first hole into which the discharge device is inserted and a second hole into which the electromagnetic wave emitter is inserted such that the housing part houses therein both the discharge device and the electromagnetic wave emitter, and the housing part can be inserted into a single hole of a cylinder head of an internal combustion engine.

An ignition unit improves an air-fuel-ratio, i.e., good mileage and lean burn without changing a gasoline engine structure significantly. The ignition unit comprises a discharge device including a booster and a discharger provided at an output side of the booster, the booster having a resonance structure configured to boost the electromagnetic wave inputted from the electromagnetic wave oscillator so as to cause a discharge from the discharger, and an electromagnetic wave emitter electrically connected to the electromagnetic wave oscillator and configured to emit the electromagnetic wave inputted from the electromagnetic wave oscillator. Moreover, the ignition unit further includes a housing part including a first hole into which the discharge device is inserted and a second hole into which the electromagnetic wave emitter is inserted such that the housing part houses therein both the discharge device and the electromagnetic wave emitter, and the housing part can be inserted into a single hole of a cylinder head of an internal combustion engine.

A method for controlling a corona ignition system in which a corona discharge is produced at an ignition electrode by exciting a resonating circuit with an AC voltage produced by a high-frequency generator. The AC voltage is adjusted to a target value depending on an operating state of the engine. Combustion onset is determined by evaluating an electrical variable of the resonating circuit and the target value of the AC voltage is reduced by a predefined value following a predefined number of engine cycles or a predefined operating period. The determined combustion onset is evaluated in one or more engine cycles. The target value for the momentary engine operating state is then increased if, by evaluation of the combustion onset, it is found that a predefined requirement is no longer met. Otherwise, the reduced target value is stored as a new target value for the momentary engine operating state.

A method for controlling a corona ignition system in which a corona discharge is produced at an ignition electrode by exciting a resonating circuit with an AC voltage produced by a high-frequency generator. The AC voltage is adjusted to a target value depending on an operating state of the engine. Combustion onset is determined by evaluating an electrical variable of the resonating circuit and the target value of the AC voltage is reduced by a predefined value following a predefined number of engine cycles or a predefined operating period. The determined combustion onset is evaluated in one or more engine cycles. The target value for the momentary engine operating state is then increased if, by evaluation of the combustion onset, it is found that a predefined requirement is no longer met. Otherwise, the reduced target value is stored as a new target value for the momentary engine operating state.

An ignition device is provided, the ignition device comprises a coaxial structural body comprising an inner conductor 2, an outer conductor 3, and an insulator 4 that insulates both the conductors 2 and 3, which are coaxially provided with one another along an axial direction. A connection terminal 5 is arranged at one axial end side of the coaxial structural body and connecting the inner conductor 2 and the outer conductor 3 to the electromagnetic wave oscillator MW. The inner conductor 2 has a linearly extended part protruding at another axial end side of the coaxial structural body extending outwards from the outer conductor 3 in the axial direction and a spirally extended part continuously extending from the linearly extended part in a reversed direction and in a spiral manner that winds around the linearly extended part of the inner conductor 2 in a predetermined number of turns around the linearly extended part such that the inner conductor 2 forms a resonance structure and the spirally extended part 20 with the resonance structure is obtained. A diameter and a length of the inner conductor 2 that is extended outwards from the outer conductor 3, and the number of turns of the spirally extended part of the inner conductor 2 are determined such that a capacitive reactance XC and an inductive reactance XL of the spirally extended part are substantially equal to each other.

An ignition device is provided, the ignition device comprises a coaxial structural body comprising an inner conductor 2, an outer conductor 3, and an insulator 4 that insulates both the conductors 2 and 3, which are coaxially provided with one another along an axial direction. A connection terminal 5 is arranged at one axial end side of the coaxial structural body and connecting the inner conductor 2 and the outer conductor 3 to the electromagnetic wave oscillator MW. The inner conductor 2 has a linearly extended part protruding at another axial end side of the coaxial structural body extending outwards from the outer conductor 3 in the axial direction and a spirally extended part continuously extending from the linearly extended part in a reversed direction and in a spiral manner that winds around the linearly extended part of the inner conductor 2 in a predetermined number of turns around the linearly extended part such that the inner conductor 2 forms a resonance structure and the spirally extended part 20 with the resonance structure is obtained. A diameter and a length of the inner conductor 2 that is extended outwards from the outer conductor 3, and the number of turns of the spirally extended part of the inner conductor 2 are determined such that a capacitive reactance XC and an inductive reactance XL of the spirally extended part are substantially equal to each other.

In order to transmit high frequency energy to a coupling circuit, if the high frequency energy is transmitted via a harness provided with a high-voltage cable, the loop in which the high frequency energy is conducted is long, and thus, noise occurring from the loop is increased. Thus, shielding is needed to be provided to the entire apparatus. The present invention has a structure in which: a high frequency energy supply circuit and a coupling circuit are connected by a connection member; and a housing having therein the high frequency energy supply circuit is integrated with a housing having therein the coupling circuit. Accordingly, the entire apparatus can be downsized and noise occurring from the loop can be reduced.

An ignition system for an internal combustion engine has a power source, a transformer having first and second primary windings and a secondary winding, a connector extending from the secondary winding and adapted so as to connect with a terminal of the spark plug of the internal combustion engine, and electronic spark timing circuit cooperative with the transformer so as to activate and deactivate voltage to the first and second primary windings. The first and second primary windings are connected to the power source such that the transformer produces an alternating voltage output from the secondary winding of between 1 kHz and 100 kHz and a voltage of at least 20 kV. A forced push-pull inverter is cooperative with the electronic spark timing circuit so as to fix a frequency of voltage to the first and second primary windings.

A high-frequency discharge ignition device includes a current supply device which supplies an AC current to a spark discharge path formed in a gap of an ignition plug, a control device which controls the operation of the current supply device, and a voltage detection device which outputs a signal of a section where a magnetic induction voltage of a primary coil generated after a switch element of an ignition coil device is placed in a shutoff state exceeds a predetermined voltage, and the control device determines the timing when the spark discharge path has been formed in the gap of the ignition plug according to an output signal of the voltage detection device and operates the current supply device based on the timing when the spark discharge path has been formed in the gap of the ignition plug to supply the AC current to the spark discharge path.